1. Field of the Invention
The present invention relates to a valve timing control device.
2. Description of Related Art
A vane-type valve timing control device is known in which a camshaft is driven by a crankshaft of an internal combustion engine via a timing pulley synchronously rotated with the crankshaft and a chain sprocket. At least one of an intake valve and an exhaust valve is opened/closed with a phase difference based on a relative rotation between the camshaft and the timing pulley or the chain sprocket. In the vane-type valve timing control device, a vane rotor having vanes is rotatably accommodated in a housing member, so that axial end surfaces of the vane rotor are in a sliding contact with respective inner surfaces of the housing member. An advancing oil chamber is formed on one side of the vane in a rotational direction, while a retarding oil chamber is formed on the other side of the vane in the rotational direction.
When a sliding clearance between the vane rotor and the housing member is large, a part of working fluid may get out from the advancing oil chamber to the retarding oil chamber, or vice versa. This phenomenon is called as an internal leakage. When the internal leakage occurs, oil pressure from an oil pump cannot be effectively used for controlling the valve timing. As a result, energy efficiency may be decreased and accuracy for phase control by valve opening/closing timing may be decreased.
The sliding clearance includes a radial clearance between an outer periphery of the vane rotor and an inner periphery of the housing member and a thrust clearance between the axial end surfaces of the vane rotor and the inner surfaces of the housing member. A seal member and a plate spring have been used in the art for suppressing the internal leakage via the radial clearance.
In contrast, as an art for suppressing the internal leakage via the thrust clearance, in a valve timing control device described in JP 3567551B2, a sealing plate having a convex elastic member contacts an end face of a vane rotor, so as to restrict the internal leakage.
A valve timing control device may further include a stopper pin corresponding to a regulating portion that regulates a relative rotation between a vane rotor and a housing member at a most advanced position or a most retarded position. When a predetermined oil pressure is not supplied to the valve timing control device such as an engine starting timing, the stopper pin regulates the relative rotation between the vane rotor and the housing member even when a cam torque is generated by a rotation of a camshaft.
FIG. 4 of JP 3567551 B2 illustrates a structure that a tip end of the stopper pin is fitted into a stopper hole defined in a front plate. In such valve timing control device having the sealing plate, it is necessary that a fitting hole is provided on the opposite side of the sealing plate and that the tip end of the stopper pin is fitted into the fitting hole. Alternatively, an escape hole into which the tip end of the stopper pin passes may be defined in the sealing plate, and a fitting hole may be defined on the opposite side of the sealing plate relative to the stopper pin. In both cases, the fitting hole is necessary to be defined in a member other than the sealing plate, so that the number of components and the number of manufacturing processes are increased.